added checkrwlc

	checkrwlc is an implemntation of the algorithm proposed by
	M. de Kool and U. Anzer (1993), MNRAS, 262, 726. It is a simple
	possibilty to check if a given pulse period evolution is following
	a random walk.
	This is a alpha version of the script, but should work. Monte Carlo
	Simulations using this script will be coming soon.